DNA replication

• What is semi conservative replication?

  -DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand.

  -It ensures genetic continuity between generations of cells
• The steps of semi conservative replication:

  • The double helix unwinds
  • the hydrogen bonds between complementary bases break, using DNA helicase which separates the two strands
  • Both strands are used as templates
  • Complementary free nucleotides bind to the bases through hydrogen bonding
  • Adjacent nucleotides are joined by phosphodiester bonds by DNA polymerase
• What is conservative DNA replication?

  The entire original DNA double helix serves as a template for the new double helix
• Evidence for semi conservative DNA replication

  • Meselson and Stahl moved E.coli from the 15N batch to a solution containing 14 N only
  • They found after one generation of growth in 14N, the single band observed was in the space between DNA of cells grown exclusively in 15 N and 14N
  • Meaning that semi conservative replication must be correct as in this case the new DNA being produced was mixture of the 14N and 15N (had strands of 14N and free nucleotides strands of 15N and other free nucleotides )